Mumbai: Prime Minister Narendra Modi on Saturday laid foundation stones of many key infrastructure projects, including the country's longest sea bridge and two metro lines in the city, entailing investment of over Rs 1.06 lakh crore.

"Developmental works of over Rs 1.06 trillion are getting started in a single city at a single event. This will be a big milestone in the city's history," Modi said at a public rally at the MMRDA grounds in suburban Bandra-Kurla Complex.

He kick-started progress on the much-delayed and ambitious projects, months ahead of local elections to the nation's richest civic body.

Projects include 22.5-km Mumbai Trans Harbour Link that will connect the city's eastern suburbs with the mainland across the harbour, via a 16.5 km sea bridge and a viaduct.

The Rs 17,843-crore project, for which multiple consortia have shown interest, will connect Sewri in central-east Mumbai with Nhava Sheva across the harbour which is close to the nation's largest container port JNPT.

To be completed by 2019, MTHL will also help increase connectivity to the proposed Navi Mumbai international airport.

Modi also laid the foundation stones of two new metro projects -- the 23.5-km DN Nagar-Bandra-Mankhurd Metro-2B corridor and the 32-km Wadala-Ghatkopar-Thane-Kasarvadavli Metro-4 corridor-- through a remote control at the event.

The two metro lines, part of a plan to have a 200-km metro network across the Mumbai metropolitan area cutting through densely populated suburbs serving as feeders for the island city, will be built at an investment of Rs 10,986 crore and Rs 14,549 crore, respectively.

Both the metros will run 6-coach trains and is expected to carry 1,800 commuters per trip each.

The Mumbai Metropolitan Region Development Authority is aiming to reduce the overcrowding in suburban local trains run through these metro projects and also reducing the vehicular traffic woes.

The Prime Minister also laid the foundation stone for multiple works to be carried out as part of the third phase of the Mumbai Urban Transport Project with an investment of Rs 52,000 crore across the megapolis.

Major among these are suburban networks including two more lines between Virar-Dahanu Road, Panvel-Karjat double line suburban corridor and trespass control at 22 locations.

Modi also laid the foundation stone for flyovers to ease traffic congestion at critical spots which include two flyovers at Bandra's Kalanagar Junction.

He also laid the foundation for a Rs 3,600-crore grand memorial for Shivaji Maharaj, the 17th century warrior king, off the city coast.